Unusual 1-Alkyne Dimerization/Hydrogenation Sequences Catalyzed by [Ir(H)2(NCCH3)3(P-i-Pr3)]BF 4: Evidence for Homogeneous-Like Mechanism in Imidazolium Salts

Janeth Navarro, Mária Sági, Eduardo Sola, Fernando J. Lahoz, Isabel T. Dobrinovitch, A. Kathó, Ferenc Joó, Luis A. Oro

Research output: Contribution to journalArticle

33 Citations (Scopus)

Abstract

The reaction of complex [Ir(H)2(NCCH3) 3(P-i-Pr3)]BF4 (1) with excess of 1-alkynes such as t-BuC ≡ CH and PhC ≡ CH gave the butadiene compounds Ir[η4-(R)2C4H4](NCCH 3)2(P-i-Pr3)}BF4 (R = t-Bu, 5; R = Ph, 6). Compound 5 was obtained as a single isomer containing a 1,3-disubstituted butadiene ligand, whereas 6 was formed as a 7:1 mixture of isomers containing 1,3- and 1,4-disubstituted butadienes, respectively. Spectroscopic observations showed alkenyl hydride reaction intermediates, consistent with a double insertion/C-C coupling sequence. Complexes 5 and 6 were found to react with dihydrogen to give 1 and alkenes resulting from the partial hydrogenation of the butadiene moieties. This dimerization/ hydrogenation sequence has been found to be the major reaction of t-BuC ≡ CH under conditions of homogeneous hydrogenation whereas that of PhC ≡ CH produced styrene and ethylbenzene as major products. Similar selectivity was observed for these hydrogenations using organic/ionic liquid biphasic conditions with toluene/ BMIM · BF4, suggesting reaction mechanisms similar to those operating under homogeneous conditions. This conclusion is also supported by the spectroscopic observation of alkenyl hydride intermediates during the formation of 6 in BMIM · BF4 as solvent.

Original languageEnglish
Pages (from-to)280-288
Number of pages9
JournalAdvanced Synthesis and Catalysis
Volume345
Issue number1-2
Publication statusPublished - Jan 2003

Fingerprint

Alkynes
Dimerization
Butadiene
Hydrogenation
Salts
Hydrides
Isomers
Butadienes
Ionic Liquids
Reaction intermediates
Styrene
Ethylbenzene
Toluene
Alkenes
Ionic liquids
Olefins
Ligands
1,3-butadiene
1-butyl-3-methylimidazolium tetrafluoroborate

Keywords

  • Alkynes
  • Biphasic catalysis
  • Homogeneous catalysis
  • Hydrogenation
  • Ionic liquids
  • Iridium

ASJC Scopus subject areas

  • Chemistry (miscellaneous)
  • Organic Chemistry
  • Catalysis

Cite this

Unusual 1-Alkyne Dimerization/Hydrogenation Sequences Catalyzed by [Ir(H)2(NCCH3)3(P-i-Pr3)]BF 4 : Evidence for Homogeneous-Like Mechanism in Imidazolium Salts. / Navarro, Janeth; Sági, Mária; Sola, Eduardo; Lahoz, Fernando J.; Dobrinovitch, Isabel T.; Kathó, A.; Joó, Ferenc; Oro, Luis A.

In: Advanced Synthesis and Catalysis, Vol. 345, No. 1-2, 01.2003, p. 280-288.

Research output: Contribution to journalArticle

Navarro, Janeth ; Sági, Mária ; Sola, Eduardo ; Lahoz, Fernando J. ; Dobrinovitch, Isabel T. ; Kathó, A. ; Joó, Ferenc ; Oro, Luis A. / Unusual 1-Alkyne Dimerization/Hydrogenation Sequences Catalyzed by [Ir(H)2(NCCH3)3(P-i-Pr3)]BF 4 : Evidence for Homogeneous-Like Mechanism in Imidazolium Salts. In: Advanced Synthesis and Catalysis. 2003 ; Vol. 345, No. 1-2. pp. 280-288.
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abstract = "The reaction of complex [Ir(H)2(NCCH3) 3(P-i-Pr3)]BF4 (1) with excess of 1-alkynes such as t-BuC ≡ CH and PhC ≡ CH gave the butadiene compounds Ir[η4-(R)2C4H4](NCCH 3)2(P-i-Pr3)}BF4 (R = t-Bu, 5; R = Ph, 6). Compound 5 was obtained as a single isomer containing a 1,3-disubstituted butadiene ligand, whereas 6 was formed as a 7:1 mixture of isomers containing 1,3- and 1,4-disubstituted butadienes, respectively. Spectroscopic observations showed alkenyl hydride reaction intermediates, consistent with a double insertion/C-C coupling sequence. Complexes 5 and 6 were found to react with dihydrogen to give 1 and alkenes resulting from the partial hydrogenation of the butadiene moieties. This dimerization/ hydrogenation sequence has been found to be the major reaction of t-BuC ≡ CH under conditions of homogeneous hydrogenation whereas that of PhC ≡ CH produced styrene and ethylbenzene as major products. Similar selectivity was observed for these hydrogenations using organic/ionic liquid biphasic conditions with toluene/ BMIM · BF4, suggesting reaction mechanisms similar to those operating under homogeneous conditions. This conclusion is also supported by the spectroscopic observation of alkenyl hydride intermediates during the formation of 6 in BMIM · BF4 as solvent.",
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T2 - Evidence for Homogeneous-Like Mechanism in Imidazolium Salts

AU - Navarro, Janeth

AU - Sági, Mária

AU - Sola, Eduardo

AU - Lahoz, Fernando J.

AU - Dobrinovitch, Isabel T.

AU - Kathó, A.

AU - Joó, Ferenc

AU - Oro, Luis A.

PY - 2003/1

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N2 - The reaction of complex [Ir(H)2(NCCH3) 3(P-i-Pr3)]BF4 (1) with excess of 1-alkynes such as t-BuC ≡ CH and PhC ≡ CH gave the butadiene compounds Ir[η4-(R)2C4H4](NCCH 3)2(P-i-Pr3)}BF4 (R = t-Bu, 5; R = Ph, 6). Compound 5 was obtained as a single isomer containing a 1,3-disubstituted butadiene ligand, whereas 6 was formed as a 7:1 mixture of isomers containing 1,3- and 1,4-disubstituted butadienes, respectively. Spectroscopic observations showed alkenyl hydride reaction intermediates, consistent with a double insertion/C-C coupling sequence. Complexes 5 and 6 were found to react with dihydrogen to give 1 and alkenes resulting from the partial hydrogenation of the butadiene moieties. This dimerization/ hydrogenation sequence has been found to be the major reaction of t-BuC ≡ CH under conditions of homogeneous hydrogenation whereas that of PhC ≡ CH produced styrene and ethylbenzene as major products. Similar selectivity was observed for these hydrogenations using organic/ionic liquid biphasic conditions with toluene/ BMIM · BF4, suggesting reaction mechanisms similar to those operating under homogeneous conditions. This conclusion is also supported by the spectroscopic observation of alkenyl hydride intermediates during the formation of 6 in BMIM · BF4 as solvent.

AB - The reaction of complex [Ir(H)2(NCCH3) 3(P-i-Pr3)]BF4 (1) with excess of 1-alkynes such as t-BuC ≡ CH and PhC ≡ CH gave the butadiene compounds Ir[η4-(R)2C4H4](NCCH 3)2(P-i-Pr3)}BF4 (R = t-Bu, 5; R = Ph, 6). Compound 5 was obtained as a single isomer containing a 1,3-disubstituted butadiene ligand, whereas 6 was formed as a 7:1 mixture of isomers containing 1,3- and 1,4-disubstituted butadienes, respectively. Spectroscopic observations showed alkenyl hydride reaction intermediates, consistent with a double insertion/C-C coupling sequence. Complexes 5 and 6 were found to react with dihydrogen to give 1 and alkenes resulting from the partial hydrogenation of the butadiene moieties. This dimerization/ hydrogenation sequence has been found to be the major reaction of t-BuC ≡ CH under conditions of homogeneous hydrogenation whereas that of PhC ≡ CH produced styrene and ethylbenzene as major products. Similar selectivity was observed for these hydrogenations using organic/ionic liquid biphasic conditions with toluene/ BMIM · BF4, suggesting reaction mechanisms similar to those operating under homogeneous conditions. This conclusion is also supported by the spectroscopic observation of alkenyl hydride intermediates during the formation of 6 in BMIM · BF4 as solvent.

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KW - Biphasic catalysis

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KW - Iridium

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